Convert Millimeters to Nanometers

The Millimeter (symbol: mm) is a unit of surface roughness. A roughness unit equal to exactly 1,000 μm — used for very coarse surfaces where μm-Ra would produce unwieldy 4-5 digit numbers: sand-cast metal surfaces before machining cleanup (cast-iron sand-cast Ra typically 0.5-3 mm = 500-3,000 μm), raw cut-off saw and oxyacetylene-cut steel surfaces in steel fabrication, weld-bead surface finish before grinding, and most importantly the absolute roughness ε of pipe inner walls in fluid-mechanics Darcy-Weisbach pipe-flow friction calculations per the Moody diagram / Colebrook-White equation. Standard pipe-roughness reference values per Crane Technical Paper 410 / ASHRAE Handbook Fundamentals chapter 22: drawn copper tubing ε = 0.0015 mm (1.5 μm); commercial steel pipe ε = 0.045 mm; galvanized iron ε = 0.15 mm; cast iron ε = 0.26 mm; concrete pipe ε = 0.3-3.0 mm; riveted steel pipe ε = 0.9-9.0 mm. These mm ε values are used directly in the Colebrook equation 1/√f = -2·log₁₀(ε/(3.7D) + 2.51/(Re·√f)) to compute friction factor f for any pipe Reynolds number Re and diameter D. HVAC duct designers per ASHRAE 90.1 and water-distribution engineers per AWWA M11 standards use mm pipe roughness daily.

It belongs to the metric measurement system.

Millimeters are commonly used in machining, quality control, and tribology.

The Nanometer (symbol: nm) is a unit of surface roughness. A surface-roughness unit equal to exactly 0.001 μm = 10⁻⁹ m. Nanometer-level roughness specification (typically reported as nm Rq RMS, not nm Ra) is required for: precision optical surfaces (mirrors for large-aperture telescopes per ESO E-ELT primary-mirror specification < 1 nm RMS over relevant spatial frequencies; EUV lithography photomask substrates for ASML scanners 0.2-0.5 nm RMS per SEMI P37 / P38 specifications), silicon wafer manufacturing (300 mm prime wafers achieve 0.1-0.3 nm Ra over the polished surface after CMP per SEMI M1 standard), and high-performance hydrodynamic / hydrostatic precision bearings (turbomolecular vacuum pump bearings, atomic-clock-grade reference flats). Atomic-Force Microscopy (AFM — Bruker Dimension Icon, Park Systems NX, Asylum MFP-3D) and white-light interferometry (Zygo, Bruker, Sensofar) resolve surface variations down to sub-nanometer (<0.1 nm RMS) over micrometer-scale fields. The IUPAC 2014 official roughness conversion convention recommends nm only when the underlying measurement instrument resolves <10 nm features — otherwise μm is preferred. Used heavily in EUV photomask qualification, optical-table flat-mirror specs, and semiconductor wafer-flatness GBIR/SFQR metrics.

It belongs to the metric measurement system.

Nanometers are commonly used in machining, quality control, and tribology.